The invention relates to a method for fixing an adjusting device on a disc brake, in particular a pneumatically actuated disc brake.
Pneumatically actuated disc brakes have over time become standard equipment on heavy commercial vehicles. Such disc brakes require mechanical boosting or “force amplification” in order to produce the demanded brake application force, because the force of the pneumatically charged brake cylinders is restricted on account of the pressure level (at present approximately 10 bar) and the limited structural size of the brake cylinder. Presently known pneumatically actuated disc brakes have boost ratios of between 10:1 and 20:1. The piston strokes of the brake cylinders are in the range from 50 mm to 75 mm, resulting in brake application travels of approximately 4 mm for pressing the brake pads against the brake disc.
The friction material thickness of the brake pads lies in the range of 20 mm, and because two pads are installed, this results in a wear travel of approximately 40 mm, not taking disc wear into consideration. This travel is a multiple greater than the abovementioned brake application travel. It is therefore necessary for the brake to be adjusted correspondingly to the pad wear by means of a device. The prior art provides automatic wear adjustment by which the so-called air play, that is to say the gap between the brake pads and the brake disc in the non-actuated state, is kept constant independently of the wear state and wear behavior of the brake pads.
In commercial vehicles, use is very often made of disc brakes which have a wear adjustor which is arranged concentrically in the cavity of a threaded spindle and which is driven eccentrically by the brake lever via a drive element (shift finger). During a braking process, the brake lever which is coupled to the piston rod of the brake cylinder performs a rotational movement. Before the rotational movement of the rotary lever is introduced into the adjustor via the coupling mechanism of the adjusting device (shift fork and shift finger), a so-called idle travel must be overcome. This travel is decisive of the size of the so-called air play, because during the movement, the adjustment is not activated, and the brake application travel therefore constitutes the air play. After the idle travel is overcome, the adjustor is set in a rotational movement, and an adjusting process is initiated by the coupling to the threaded spindle or tube.
Adjusting devices for disc brakes exist in various embodiments. DE 10 2004 037 771 A1 (having U.S. counterpart published application US2007/209890 A1) discloses an adjusting device for a disc brake, the specifications of which are expressly incorporated by reference herein. The adjusting device is suitable for a pneumatically actuated disc brake, in particular one of sliding-caliper design. Furthermore, the adjusting device can, however, also be used in pneumatically actuated fixed-caliper or pivoting-caliper disc brakes.
DE 10 2004 037 711 A1 describes an adjustor of the type, which is shown in FIG. 5. The adjustor is composed substantially of the following functional elements: shaft 2; bearing disc 3; axial bearing 5; collar bush, or spacer sleeve 19; shift fork, or drive ring 6; ball ramp clutch 7; cone clutch 17; and cylindrical spring 12. With regard to the description, reference is made to DE 10 2004 037 711 A1 (US 2007/209890 A1).
The adjusting device must basically perform two functions:
1. the automatic air play adjustment; and
2. the manual restoration or retraction of the adjusting mechanism upon renewal of the brake linings.
In order that the function of the wear adjusting device is ensured for an automatic adjustment process during braking and for a manual restoration when replacing brake pads, it is necessary for the adjusting device to be fixed in the brake caliper and positioned relative to the brake lever.
In the light of production tolerances and the relatively high degree of variation of mass-produced components, individual positioning and fixing of the adjusting device is problematic.
It is therefore necessary, when installing the adjusting device into the brake, for the fixing of the adjusting device to be carried out correspondingly to the existing tolerance situation. The present state of the art is rotational fixing by use of a lug on the bearing disc of the adjusting device and a corresponding pocket in the brake caliper. With this arrangement, however, it is not possible to individually position the adjusting device. To permit individual positioning, therefore, a locking method is required which has a capacity for adaptation.
Corresponding methods would, for example, be welding or adhesive bonding. In the case of welding, however, there is the difficulty that this can be integrated within an assembly process only with a high level of expenditure (protection from radiation and welding gases). Furthermore, the welding of different materials, such as in this case nodular graphite iron and steel, is relatively difficult.
In the case of adhesive bonding, the surfaces must be very clean and free from grease, and ensuring this is likewise associated with a very high level of expenditure, because numerous components must be assembled with grease for their permanent function.
Both methods also have the disadvantage that disassembly is difficult or impossible.
It is therefore the object of the present invention to provide an improved method for fixing an adjusting device to a disc brake, with the above disadvantages being eliminated or significantly reduced, and further advantages being obtained.
This and other objects are achieved by a method for fixing an adjusting device on a disc brake, in particular, a pneumatically actuated disc brake, as well as by a correspondingly assembled disc brake. The method includes the steps of: (a) inserting the adjusting device in a previously set rest position into an adjusting spindle of the disc brake, with a drive ring of the adjusting device being coupled to a rotary lever of the disc brake and with centering being provided by a bearing disc of the adjusting device in a receptacle of a brake caliper; (b) positioning the adjusting device by turning the latter; and (c) fixing the adjusting device to the disc brake by locking the bearing disc to the brake caliper by way of a locking element.
By use of the method according to the invention, fixing of the adjusting device is carried out, after positioning has taken place, by virtue of a locking element, for example a ball or a short cylindrical pin, being pressed into a recess of a brake caliper of a disc brake.
The pressing-in of the ball results firstly in a pressure force between the bearing disc and caliper and secondly in a positive-fitting connection as a result of the deformation on the bearing disc. A reliable, permanent anti-twist facility for the adjusting device is ensured in this way. Disassembly is likewise possible with this fastening method.
The adjusting device is firstly inserted, in a previously set rest position, into an adjusting spindle of the disc brake, with a drive ring (for example with a shift fork) of the adjusting device being coupled to a rotary lever of the disc brake and with centering being provided by a bearing disc of the adjusting device in a receptacle of a brake caliper. The adjusting device is then individually positioned by turning the latter, with a deformation section of the bearing disc being arranged over a recess provided in the brake caliper.
The locking element is pressed, between the bearing disc of the adjusting device and the brake caliper, into the recess. The size of the ball is selected such that, on the caliper, the hitherto existing recess in the caliper can be used. As a result, it is not necessary to carry out any additional machining processes on the brake caliper. The bearing disc of the adjusting device or of the adjustor is designed such that sufficiently intense compression and deformation takes place without excessively high assembly forces arising in the process.
A disc brake, in particular a pneumatically actuated disc brake, having an adjusting device for adjusting for wear of the brake pads and the brake disc of a pneumatically actuated disc brake having a rotary-lever-actuated brake application device, which adjusting device can preferably be inserted into an adjusting spindle of the disc brake and attached by a bearing disc to a brake caliper, which has a recess, of the disc brake, is characterized in that the bearing disc is connected in a positive-fitting manner to the brake caliper by a locking element when the adjusting device is positioned.
The bearing disc is provided with at least one deformation section for positive-fitting connection to the brake caliper and with at least one lug for rotationally fixed connection to the adjusting device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.